THE ACIDS: Retrieving Copper Lab

*Note: filter paper weighed 1 g.

1) During investigating Matter B.3, not all of the original copper powder reacted when you heated it in air.
a. What Observational evidence leads you to think that the reaction was incomplete?
b. How would you revise the procedure so that more copper(II) oxide could form.

a. Since CuO does not react with HCl, but copper does, by adding 50 mL HCl to our beaker of 0.99 g of what we thought was pure CuO, we were able to see unconverted Cu form at the bottom of the beaker. This means that our original reaction was incomplete.
b. Maybe by exposing more of the original copper to oxygen, a more complete reaction would have occurred and more copper(II) oxide would have formed.

2) During investigating Matter B.3 (page 139),
a. what mass of the original powdered copper sample reacted when you heated it? (Hint: Refer to the original mass of copper you used during this investigation and the mass of copper residue found in Step 8 to calculate this.)
b. what percent of the total copper sample reacted?

a. Although we thought all 0.99 grams of powdered copper reacted when we heated it, retrieving the unconverted Cu, we discovered that in actuality, 0.33 g reacted.
b. 0.33/0.99 x 100% = 33%
33% of the total copper sample reacted when heated.

3) In the reaction between copper(II) chloride (CuCl2) solution and zinc metal, in Investigating Matter B.5 (page 142), each Cu^2+ ion gained two electrons to form an atom of copper metal. Each zinc metal atom lost two electrons to form a Zn^2+ ion:
a. Write a balanced chemical equation that represents this process. (Hint: to review how, turn to pages 148-150.)
b. Based on the chemical equation you wrote in Question 3a, identify
i. the reactant that was oxidized.
ii. the reactant that was reduced.
iii. the reducing agent.
iv. the oxidizing agent.

a. Zn: + Cu^2+ → Zn^2+ + Cu:
b.
i. Zn was oxidized.
ii. Cu was reduced.
iii. Zn is the reducing agent.
iv. Cu is the oxidizing agent.

4) Adding HCl to CuO, in Investigating Matter B.3 (page 139), resulted in the formation of a blue solution. This color is due to the presence of Cu^2+(aq) ions. Consult your observations when answering the following questions:
a. Describe what happened to the solution color after you added Zn (see steps 9 and 10) in this investigation.
b. What caused the changes you observed in the solution?
c. How can the color of the solution be used to indicate when the zinc metal has removed the Cu^2+ ions from the solution?

a. The color of the solution cleared and the zinc became dark red in color, and began to break apart.
b. This is because since zinc is more reactive than copper, the zinc caused copper to reduce as it oxidized in the solution.
c. Once the color was completely clear, it was an indication that the Cu^2+ ions in the solution had reduced into solid Cu. The zinc had oxidized and became Zn^2+ ions in the solution.

5) To recover Cu metal from the CuCl2 solution, you had to use other resources:
a. What resources were “used up” in this recovery process?
b. Where (to what location) did each resource finally go?

a. Although the law of conservation of matter states that matter can neither be created or destroyed, Cu^2+ ions and solid Zn were “used up” in this recovery process.
b. Cu^2+ reduced into solid Cu and Zn was oxidized into Zn^2+ ions within the solution.